Studies are being carried out to examine the mechanism of action of the antitumor agent adriamycin. The major focus of this work is concerned with analyzing the mechanism by which adriamycin induces certain structural transitions in isolated chromatin. These structural changes induced in chromatin include the formation of DNA single-strand regions and a compaction and condensation of the nucleofilament. Additional studies are also being carried out to analyze certain surface membrane changes in cells resistant to the action of adriamycin.